The fact that one is submitting a story to an entire community means that users will resort to submitting stories that are either very sensationalistic or are 'funny', to appeal to the widest audience. And that's where I think Digg's flaw is. They put too much emphasis on 'making the front page', so users then adopt the motivation of submitting the most ridiculous garbage to get on the front page. On Diggnation, frequent front pagers became celebrities, and being a frequent front pager was a status symbol. Unlike here, where we're not concerned about making it in the top 10, but rather that we submit quality stuff. It really is all about the niche.